1. Field of the Invention
The present invention relates to pulse detection mechanism for detecting pulse signals outputted according to the rotation of a rotary plate having a pulse surface formed thereon. A plurality of electrically conductive areas and insulation areas are formed on the pulse surface alternately with each other. More particularly, the present invention relates to a rotation detection mechanism and in particular, a pulse detection mechanism preferably applicable to a rotation direction detection apparatus for detecting the rotational direction of a rotary member which rotates in opposite directions. More specifically, the present invention relates to a pulse detection mechanism preferably applicable to a rotation detection apparatus for detecting the rotation operation amount of a lens barrel of a camera or the like and the rotational direction of the lens barrel.
2. Description of the Related Art
A pulse detection mechanism for detecting the rotation amount and/or rotation direction of a rotary member has been hitherto utilized. The pulse detection mechanism has a substrate having a pulse surface formed thereon and brushes which contact the pulse surface. In the pulse detection mechanism, the pulse surface and the brushes rotate relative to each other in association with the rotation of the rotary member. The pulse detection mechanism detects pulse signals outputted according to the relative rotation of the pulse surface and the brushes. Various types of pulse detection mechanism have been proposed. Hitherto, brush method has been mainly adopted in this kind of pulse detection mechanism. For example, in the construction of the lens barrel disclosed in Laid-Open Japanese Patent Publication No. 4-97308, in order to detect the rotational position of a zooming ring, the pulse detection mechanism comprises the fixed circuit substrate having the pulse surface formed thereon and the brushes which cooperates with the pulse surface and rotates together with the zooming ring.
The brush method has, however, a disadvantage that errors are liable to occur in detecting the rotation amount of a rotary member and the rotational direction thereof. That is, in the brush method, a brush which contacts the pulse surface is composed of a flexible flat and long metal strip. Therefore, when the width of electrically conductive portions and that of insulation portions are small, the position of contact between the brush and the pulse surface fluctuates greatly.